Abstract : The U.S. Coast Guard's Marine Safety Office (MSO) of each port is required to develop contingency plans to respond to oil spills. The contingency plans at present do not use rigorous risk assessment procedures to identify the spectrum of spills that are possible in each port and estimate the frequency of occurrence of different size spills. In order to provide these procedures, there was a need to develop, for use in contingency planning, a uniform guidance methodology based on risk assessment principles. The development of port specific oil spill risk assessment methodology is described in this report. The port model takes into consideration the specifics of the water body in the port, vessel traffic, current or projected oil transport volume into the port per year, size distribution of vessels, as well as the size distribution of the oil carrying vessels (tankers and barges), weather and channel characteristics, etc. The model uses the accident risk factors for a number of U.S. ports developed in the Ports Need (Vessel Traffic Services Benefit) Study and takes into account the reduction in the vessel accident rate due to the provision of vessel traffic management systems. The output from the risk model is a histogram of the frequency of accidents vs the size of potential spill volume. A PC based computer program ('OlLRlSK') has also been developed to calculate the risk for any port. Using the results, the spill risks in different ports can be compared and the ports ranked based on the susceptibity to small, medium and large spills. The oil spill risk for a number of major U.S. ports has been calculated and presented. (AN)